Following publications, references and materials are used herein to illuminate the background of the invention, and they are incorporated by reference. In particular, the cases providing additional details relating to the practice are incorporated by reference.
Bioactive glass is a known bioactive material. Unlike most other bioactive materials, it is easy to control the manufacturing properties of bioactive glass, the rate of its chemical reactions and the biological response caused by it by changing the chemical composition of bioactive glass itself. Bioactive glass has been used in different types of implants, but the manufacturing of fibres from bioactive glass has been found to be difficult.
Some systems and methods for manufacturing glass fibres are disclosed in the literature. For example, document U.S. Pat. No. 3,248,192 discloses a method for the manufacture of fibres from glass, including the manufacture of several fibres at one time. The manufacturing is performed by spinning a molten glass by gravity. Document WO 2006/009802 presents a melter assembly for forming silicone crystals. The assembly comprises a melting crucible that is made of for example fused quartz that is seated on a graphite suspector assembly. The melter assembly also comprises induction coils for heating the suspector and the crucible. Publication JP 63222037 discloses the production of glass fibre by melting a glass block in a crucible and spinning molten glass through a hole in the bottom of the crucible. Publication JP 64003031 presents a method for manufacturing infrared fibres by melt spinning as the area near the nozzle is locally heated at the bottom of the crucible to keep the viscosity of the glass melt in a specific range.
Document U.S. Pat. No. 2,495,956 discloses a device and a method for making glass fibres comprising a platinum crucible placed in a furnace and heated by an induction coil. The crucible is fixed to a ceramic tube and the device also comprises a drawing unit. The method further comprises melting a glass strip in the furnace. This device and method allows the manufacture of fibres with diameters from 4.8 μm to 10 μm.
Pirhonen et al. have manufactured fibres from bioactive glass by melt spinning (E. Pirhonen, H. Niiranen, T. Niemelä, M. Brink and P. Törmälä, Manufacturing, Mechanical Characterization and In Vitro performance of Bioactive glass 13-93 fibres, Journal of Biomedical Materials Research, Applied Biomaterials Vol 77B (2) (2006) and E. Pirhonen, L. Moimas and M. Brink, Mechanical properties of bioactive glass 9-93 fibres, Acta Biomaterials Vol. 2 (2006)). One problem that was encountered in these experiments was the crystallization of the glass in the platinum crucible during glass fibre production.
Due to the crystallization during the manufacturing process when melting or reheating the glass in traditional melting furnaces the fibre drawing process is discontinuous and not suitable for production of large quantities of fibres or for the production of continuous fibres and/or for the production of very thin fibres. The temperature range where crystallization occurs cannot be avoided and it has to be passed rapidly. The temperature used for manufacturing of bioactive glass fibre is usually in the vicinity where crystallization of the glass occurs. Therefore, heating and cooling have to be done fast in order to avoid permanent crystal formation. Other problems are related to the materials of the furnace and their suitability for high temperature and biomedical requirements.